You can also consider Collection (List, Set, Map) shared between two or more Threads. One is iterating on collection and other tries to add element in it then the thread iterating over it, will throw java.util.ConcurrentModificationException

In interview if you are able to answer this question. They might me interested in checking your knowledge little bit deep. You may face the question How Fail Fast Iterator identifies that the collection is modified?Fail Safe
It iterate over the clone(copy) of original collection. So It won't throw java.util.ConcurrentModificationException.